The present disclosure relates to a nonaqueous electrolyte composition and a nonaqueous electrolyte secondary battery. In particular, the present disclosure relates to a nonaqueous electrolyte composition containing a compound having a phosphorus-hydrogen bond or phosphorus-carbon bond, and a lithium ion nonaqueous electrolyte secondary battery using the nonaqueous electrolyte composition.
Various portable electronic appliances such as camera-integrated VTRs (video-tape recorders), video cameras, digital still cameras, mobile phones, portable information terminals and laptop computers have been available in the market in recent years, and lightweight of the equipment has been desired. Consequently, research and development for improving energy density of portable power sources, particularly secondary batteries, for these electronic appliances has been actively advanced.
In general, a lithium ion secondary battery uses carbon for an anode active material, a lithium-transition metal composite oxide for a cathode active material and a carbonate ester mixture for an electrolyte solution. Such a lithium ion secondary battery has been widely used for practical applications since this battery is able to obtain a larger energy density than aqueous electrolyte secondary batteries such as a lead battery and nickel-cadmium battery in the related art (see Japanese Patent Application Laid-Open (JP-A) No. 4-332479).
However, it has been a problem that the discharge capacity maintenance factor of the lithium ion secondary battery gradually decreases by repeating charge-discharge cycles.
For solving such a problem and for improving other performances, it has been proposed to add various additives to the electrolyte solution (see JP-A Nos. 7-153487, 10-223257, 11-219711, 11-283669, 2001-202992, 2002-198090, 60-23973, 8-321313 and 2005-340161, and W O02/082575).
However, it has been difficult to obtain batteries having a sufficient discharge capacity maintenance factor even in the nonaqueous secondary batteries using the electrolyte solutions described in the above-mentioned patent publications.
Therefore, it is desirable to provide a nonaqueous electrolyte composition that can improve a discharge capacity maintenance factor after repeated charge-discharge cycles, and a nonaqueous electrolyte secondary battery using the nonaqueous electrolyte composition.